1. Field of the Invention
The present invention relates to management systems for exhaust purification apparatuses. The invention relates more particularly to a management system for an exhaust purification apparatus that purifies exhaust gases by using a filter to trap particulate matter contained in the exhaust gases and regenerates the filter by burning to remove the particulate matter trapped by the filter as appropriately.
2. Description of Background Art
Construction machines, such as hydraulic excavators, are mounted with diesel engines as their drive sources. Regulations on the amount of particulate matter (hereinafter abbreviated to “PM”), together with NOx, CO, HC, and other substances, emitted from the diesel engines have been increasingly stringent year after year. In response to such a trend in these regulations, a known exhaust purification apparatus incorporates a filter called a diesel particulate filter (hereinafter abbreviated to “DPF”) that traps PM to thereby reduce the amount of PM discharged externally. In this exhaust purification apparatus, the filter begins to clog as the amount of PM deposited therein increases. This causes engine exhaust pressure to increase, inviting degraded fuel efficiency. The PM trapped in the filter is then burned as appropriately to thereby remove clogging, so that the filter can be regenerated.
Regeneration of the filter is generally accomplished by using an oxidation catalyst. The oxidation catalyst may be disposed upstream of the filter, carried directly by the filter, or both. In either case, to activate the oxidation catalyst, the exhaust gas must have a temperature that is higher than an activating temperature of the oxidation catalyst. To achieve this end, a technique called active regeneration is known, in which the exhaust gas temperature is forced to increase to a level higher than the activating temperature of the oxidation catalyst. The active regeneration is achieved by several techniques, including one in which an auxiliary injection (post-injection) is performed to inject fuel in an expansion stroke following a cylinder main injection to thereby increase the exhaust gas temperature and one in which a regeneration fuel injection device disposed in an exhaust pipe is used to inject fuel into the exhaust gas that flows through the exhaust pipe, thereby increasing the exhaust gas temperature.
As a condition for starting the active regeneration, the foregoing techniques estimate the amount of PM deposited (the amount of PM trapped) in the filter. The regeneration is performed when the amount of PM deposited in the filter reaches a preset limit value for the amount of PM deposits. In this case, typically, a differential pressure across the filter is detected and the amount of PM deposits is calculated based on the detected differential pressure. The active regeneration of the filter may be automatic, in which case the active regeneration is automatically started, or manual, in which case the active regeneration is started by an operator input.
In the automatic active regeneration, a controller of the exhaust purification apparatus receives an input of a signal indicative of the amount of PM deposits and, when determining that the amount of PM deposits exceeds a threshold value, outputs a command signal for starting the regeneration. The exhaust purification apparatus then automatically starts regeneration. The exhaust purification apparatus automatically stops the regeneration after a predetermined period of time elapses or when determining that the amount of PM deposits is equal to or less than a predetermined value as a result of the burning removal.
There may still be cases in which PM is deposited without being properly burned and removed even through the automatic active regeneration depending on use conditions: for example, in cold areas or under similar conditions, the exhaust gas temperature may not increase to a level higher than the activating temperature; and the engine stops running in the middle of the automatic active regeneration. A technique is proposed that performs manual active regeneration that is started by an operator input in such cases (JP-2003-155914-A). In the manual active regeneration, the controller of the exhaust purification apparatus receives an input of a signal indicative of the amount of PM deposits and, when determining that the amount of PM deposits exceeds a threshold value, outputs an alarm signal prompting the regeneration. Noticing the alarm display, the operator operates a regeneration switch. Receiving the input of an operation signal, the controller of the exhaust purification apparatus outputs a command signal for starting the regeneration.
The current mainstream indicating the operating status of the hydraulic excavators and other construction machines is such that rental businesses purchase a large number of construction machines and rent them to customers who are engaged in civil engineering work as necessary. In this case, an operator as one of the customers operates the regeneration switch to perform the manual active regeneration. The PM trapped in the filter is burned and removed by an appropriate use of the operator. After using the hydraulic excavator, the customer returns the hydraulic excavator to the rental company. The rental company as an administrator services and maintains the hydraulic excavator before renting the same to another customer. If the amount of PM deposited in the filter is small upon returning of the hydraulic excavator, the rental company has only to perform a simple maintenance procedure for the exhaust purification apparatus.
The manual active regeneration may not, however, be performed properly despite the alarm display prompting the manual active regeneration for various reasons. Examples of the reasons include, but not limited to, the operator's inadvertently overlooking the alarm display of the manual active regeneration; the operator's being reluctant to consume extra fuel; and the operator's underestimating the importance of the manual active regeneration. If, as a result, there is a large amount of PM deposited in the filter upon returning of the hydraulic excavator, a service job for removing the PM becomes necessary, which results in an increased load of management in terms of work and time. The foregoing not only incurs maintenance cost, but also leads to reduced earnings as a result of aggravated turnover of rented machines. In the worst case, an amount of PM more than its limit is deposited in the filter, resulting in the exhaust purification apparatus failing or requiring a repair or replacement.
Specifically, if the operator fails to use the exhaust purification apparatus appropriately, increased load results on the part of the administrator in terms of work, time, and expenditure.